1. Technical Field
This invention has to do with disk drive suspensions, and more particularly with a head gimbal assembly (HGA) utilizing a disk drive suspension attached to the actuator arm by a preamplifier circuit chip. The invention affords the advantages of extremely short conductive paths from the head/slider to the chip with resultant substantial reduction in noise pick-up and consequent improvement in electrical performance. The invention further enables substantially increased manufacturing efficiencies in the use of preamplifier circuit chips since problems with non-chip components will not cause wastage of chips. The invention utilizes an ultra-compact suspension load beam of approximately the size of the chip to attach to the chip. The chip in turn is attached to the actuator arm.
2. Related Art
Presently known disk drive head stack assemblies (HSA) comprise a series of HGA""s arranged in a common stack. The HGA""s are connected with conductive wire or traces to a microprocessor chip comprising a central preamplifier circuit. The preamplifier circuit chip controls the read-write action of the slider (which includes the read/write head) and serves to amplify the very weak read signals coming from the slider. Read signals are often so low, e.g., less than 100 microvolts, that merely ambient electrical noise of adjacent equipment can interfere with the detection and processing of the signal. Typically, the preamplifier circuit chip has been placed on the actuator which is at a considerable remove in most suspension systems from the slider. The loss in electrical signal, however, increases with increased path length.
Placing the preamplifier chip closer to the slider presents difficulties, however, both practical and financial. For example, at least in theory, the slider can itself define a chip and provide its own preamplification. This chip-in-slider approach would require a costly development process and the sliders would likely be quite expensive. Moreover, both the chip and the slider will be lost to yield if either is defective. And one cannot tell if either is defective until installed in an HGA.
Or the chip can be placed on the suspension in a manner to be more closely adjacent the slider. This expedient reduces the length of the electrical path for the lowest amplitude signals, reducing noise exposure and lowering the probable error rate. There is the disadvantage, however, of having the chip premounted on the suspension delivered to the disk drive manufacturer and unusable if the suspension for unrelated reasons is not within specifications, wasting the costly chip. Or, the disk drive manufacturer can as part of the drive build add the chip to the suspension. In the chip-on-suspension approach, if the chip is added to the suspension before the slider is added, (which appears necessary since the chip cannot practically be added after the slider is added) the impact on yield of HGA assemblies is greater and the cost more expensive because the scrapped parts represent more value. It is advantageous to add the most expensive components of the suspension as late as possible in the build process after as many of the early step yield losses have already occurred. But, mounting the chip on the suspension before adding the slider obviates this advantage and increases the cost of the discarded assembly, should it be necessary to discard, by the amount involved in acquiring and installing the later discarded chip. The chip-on-suspension approach places the mass of the chip along the middle length of the load beam, and the suspension thus suspends the chip mass. This lowers the resonant frequency of the suspension and provides only lower shock resistance, unlike the invention suspension which places the mass of the chip between the suspension and the actuator arm. Further, the placement of the chip on the load beam is disadvantageous in that the chip so placed is subject to all the physical action of the load beam from bending, twisting, shock and other forces.
It is an object therefore of the present invention to provide improvements in suspension design. It is a further object to provide a novel HGA design having a suspension supported by the preamplifier circuit chip. Another object is the provision of an HGA in which the electrical leads are greatly shortened between the slider and the preamplifier chip to obtain read signals less subject to noise and attentuation. A still further object is to provide a novel suspension and chip combination which affords all the benefits of the optimum relative placement of the slider and chip, and preserves the suspension gimballing function, while only lengthening the actuator arm that supports the chip and slider combination. Other objects will appear hereinafter.
In the present invention an ultra-compact suspension is preferably used, one occupying as little as one-third or even less lateral area as a conventional small size suspension. The suspension is so small that it is feasible to attach the suspension to the actuator arm by the preamplifier chip. The invention suspension can be used with magnetic or optical heads and associated sliders.
These and other objects of the invention to become apparent hereinafter are realized in the combination of a preamplifier circuit chip and a disk drive suspension assembly of a slider, a flexure, a load beam and a mounting plate, all in operative association; the preamplifier circuit chip supporting the assembly on a disk drive actuator arm.
In this and like embodiments, typically: the assembly mounting plate is adhered to the preamplifier circuit chip, the preamplifier circuit chip being adhered to the actuator arm to support the assembly at the actuator arm; the assembly mounting plate is adhered to the preamplifier chip, or the preamplifier circuit chip has a plurality of support legs extending therefrom, the preamplifier circuit chip being attached to the actuator arm by the support legs to support the assembly at the actuator arm; the assembly and preamplifier circuit chip are disposed in a common stack; the load beam at least partially surrounds the flexure, and the mounting plate is attached to the load beam in flexure bridging relation, the preamplifier circuit chip being attached to the mounting plate at the locus of the flexure-bridging; and, the preamplifier circuit chip and load beam are each generally rectangular and of substantially the same area.
In a further embodiment, the invention provides a disk drive suspension assembly adapted for mounting to a disk drive actuator arm, the suspension assembly comprising a flexure for supporting a slider in operative association with a disk, a load beam supporting the flexure, a mounting plate, and a preamplifier circuit chip having a first surface to which the mounting plate is mounted and a second surface adapted for mounting the preamplifier circuit chip to the actuator arm.
In this and like embodiments, typically: the flexure, the slider, the load beam, the mounting plate, and the preamplifier circuit chip are arrayed in a common stack relation; the mounting plate is adhered to the preamplifier circuit chip, and includes also a disk drive actuator arm, the preamplifier circuit chip being adhered to the actuator arm to support the suspension assembly at the actuator arm, or the mounting plate is adhered to the preamplifier circuit chip, the preamplifier circuit chip having a plurality of support legs extending therefrom, and includes also a disk drive actuator arm, the preamplifier circuit chip being adhered to the actuator arm by the support legs; the load beam at least partially surrounds the flexure, and the mounting plate is attached to the load beam in flexure bridging relation, the preamplifier circuit chip being attached to the mounting plate at the locus of the flexure-bridging; the preamplifier circuit chip and load beam are each generally rectangular, are of like surface area, and opposed in the stacked condition of the suspension; there is also included an actuator arm and disk, the actuator arm extending longitudinally in a predetermined first plane generally parallel with the disk; the flexure, load beam, mounting plate and preamplifier circuit chip being arrayed in a common stack extending within a cylindrical second plane, the cylindrical plane intersecting the actuator arm plane; the cylindrical second plane intersects the actuator arm first plane at a right angle; the cylindrical second plane has a diameter sufficient to surround the common stack and no greater than three times the diameter necessary to surround the preamplifier circuit chip in the common stack; the assembly mounting plate is adhered to the preamplifier circuit chip, the preamplifier circuit chip being adhered to the actuator arm to support the assembly at the actuator arm; the load beam at least partially surrounds the flexure, and the mounting plate is attached to the load beam in flexure bridging relation, the preamplifier circuit chip being attached to the mounting plate at the locus of the flexure-bridging; and, the preamplifier circuit chip and load beam are each generally rectangular and of substantially the same surface area.
Preferably, the load beam has generally an E-shape with a base, and extending from the base a center portion, a left portion and a right portion all generally extending in a load beam plane, the flexure generally extends in a flexure plane spaced from and generally parallel to the load beam plane, the flexure being attached to the left and right load beam portions and in gimballing contact with the load beam, a slider supported by the flexure for operative association with the disk, and a mounting plate extending in a mounting plate plane spaced from and generally parallel to the flexure plane, the mounting plate being attached to the load beam at its the left and right portions only to bridge the flexure; the mounting plate is centrally deflected, the mounting plate being adhered to the preamplifier circuit chip at the deflection; and the suspension is provided in further combination with electrical leads attached between the preamplifier circuit chip and the slider head, and from the preamplifier circuit chip to suspension control electronics.
In its method aspects the invention provides the method of assembling a disk drive suspension and preamplifier circuit chip combination, including arranging the slider, the flexure, the load beam and the mounting plate in stacked and interconnected relation, attaching a preamplifier circuit chip to the mounting plate, and attaching the preamplifier circuit chip to an actuator arm.